In the passive geo-location methods, the relative altitude between the target and the UAV can't be measured directly. In this paper, the projection model is established to deal with the location without altitude and estimate the height. For the measurement error will significantly increase the locate uncertainty, the Recursive Least Square (RLS) estimation is used to estimate the target position and the relative height. The RLS estimation can give an unbiased estimator of the target position which means the target locate accuracy can be greatly improved by accumulating a large quantity of measure points. Simulation results have verified the efficiency of the method.